The proposed study's focus is to develop assessment tools for bipolar illness in prepubertal children. As bipolar illness has only recently been recognized as a legitimate psychiatric disorder among a prepubertal population assessment instruments are limited. This is of significant concern, both to clinicians who provide routine evaluation and management of bipolar children, and to researchers attempting to determine the most appropriate type and intensity of treatment for these children. Underdiagnosis of the disorder has been documented in children. Weller, et al. reported 50% of children diagnosed in their study as manic originally received some other diagnosis, most commonly schizophrenia. They stress the need to consider mania in the deferential diagnosis of psychotic children (1986a). Research conducted to date on bipolar children is noted for its lack of systematic behavioral observations. Thus, without valid and reliable tools to assess bipolar illness in children, accuracy in diagnosis, appropriateness of subsequent care, and research regarding mental health services to children with bipolar disorder will be hindered. Although clinical rating scales to assess and monitor mania are commonly used with adult populations, no such scales have been developed for or tested specifically in prepubertal children. To be most useful, such scales should be able to discriminate manic from hyperactive children, as this is an especially difficult discrimination to make. Therefore, the purpose of this study is to develop more precise instruments to assess bipolar illness in prepubertal children. these instruments should be designed such that they can be used both in the regular management of bipolar children and in research to examine the efficacy of service delivery to these children. To accomplish this, the following psychometric properties of two mania rating scales, the Mania Rating Scale and the Clinical Global Impression--Mania will be determined in a prepubertal population: optimal cut-off scores, sensitivity, specificity, predictive value, diagnostic confidence, sensitivity to change in clinical status, test-retest reliability, internal consistency, convergent validity, and discriminant validity. Bipolar children will be compared at baseline on these as well as other previously validated instruments to children with attention deficit hyperactivity disorder (ADHD) alone, ADHD and conduct disorder, unipolar major depression, schizophrenia, and to normal control children. All six groups will be reassessed six weeks later. This study should provide essential data regarding the reliability, validity, and utility of two rating scales to assess mania. This information should be beneficial to mental health service providers as they assess, treat, and study treatment efficacy of bipolar illness in children.